Method for detecting portable objects and system for carrying out said method

ABSTRACT

A method for detecting portable objects from a network of N antennae controlled by a centralized management unit. Signals are simultaneously emitted by the management unit to all antennae. Resulting response signals from antennae that have detected a portable object are received by the management unit. Each object thus detected is successively selected from these signals according to a pre-established sequence. The invention applies in particular to access control.

This disclosure is based upon, and claims priority from FrenchApplication No. 99/01521, filed on Feb. 9, 1999 and InternationalApplication No. PCT/FR00/00230, filed Jan. 31, 2000, which was publishedon Aug. 17, 2000 in a language other than English, the contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method of detecting portable objects using anetwork of N antennae and a detection system implementing the saidmethod.

Hereinafter antenna means the antenna itself but also the electronics,associated with the said antenna, for transmitting and receivingsignals.

Portable object means any information carrier of the smart card typeprovided with an antenna, or any electronic label.

Generally antennae are put in a network when the management unitresponsible for taking a decision has to be centralised. This is forexample the case when it is sought to effect a physical access controlfor a dwelling, or access control in the case of a public building. Itis also the case when it is wished to keep a trace on an object in adatabase.

Putting antennae in a network makes it possible not to duplicate theintelligence of the system and reduces the costs of the installation.Use will therefore be made, for this purpose, of a management systemincluding a unit for the centralised management of the network.

Such an organisation is not without difficulties. This is because thecentralisation of the intelligence of the system gives rise to problemsrelated in particular to the operating mode of the management unit.

At the present time, putting N antennae in a network is managed by ascrutiny algorithm which successively selects the antennae in order tocheck the presence of a portable object. The major drawback of thissolution is that an antenna is selected even if no portable object ispresented to it. This therefore gives rise to a loss of timeproportional to the number of antennae in the network, and prevents themanagement unit from devoting itself to other tasks.

Where several portable objects are detected by the same antenna, themanagement unit manages this situation by means of an anti-collisionalgorithm in order to select the portable objects which have beendetected by this antenna, one after the other.

When the unit has finished communicating with the portable objects bymeans of this antenna and when it has adjusted the phenomena ofcollision on this antenna, it passes to another antenna.

Thus, if a network of 64 antenna, for example, is considered, theminimum time for detecting a portable object in front of an antennabeing 25 milliseconds, each antenna is interrogated every 1.6 seconds(64×25 milliseconds).

Where such a system is used in access control, a user must wait up to1.6 seconds before obtaining a response from the detection system.

The centralisation of the management unit therefore gives rise toproblems, notably the problems set out below:

-   -   an increase in the complexity of the system due to the        management of the scrutiny,    -   the reaction time extended by the scrutiny of the antennae,    -   the complex installation, since the management unit must know        the configuration of the network,    -   the antennae are interrogated even if no object is presented,    -   the number of antennae in the system is limited by the scrutiny        time.

The purpose of the present invention is to remedy these problems.

SUMMARY OF THE INVENTION

The first object of the invention is a method of detecting portableobjects making it possible to manage a large number of antennae in amanner which is transparent for the management unit.

According to the invention, the management unit must also be providedwith a means of successive selection of each portable object detected bythe antennae, this means preferably consisting of an anti-collisionalgorithm, which may be conventional per se.

One object of the invention is more particularly a method of detectingportable objects using a network of N antennae, controlled by acentralised management unit, principally characterised in that itincludes the following steps:

-   -   the transmission by the management unit of signals        simultaneously to all the antennae,    -   the reception by the said unit of a resulting signal comprising        response signals from the antennae which have detected a        portable object,    -   the successive selection of each object detected from this        resultant signal, according to a pre-established sequence.

According to another characteristic, the successive selection of eachobject is effected by the use of an anti-collision algorithm.

According to a variant, the reception of the resulting signal by themanagement unit is obtained by the reception of the response signalsfrom the antennae respectively at the input point of the unit reservedfor each antenna and the adding of the said signals.

According to another variant, the reception of a resulting signal by themanagement unit is obtained by the reception of the said resultingsignal at an input point of the unit reserved for all the antennae inthe network.

According to a variant, the reception of the resulting signal includes astep of identifying the origin of the response signals forming the saidresulting signal.

The identification of a response signal includes a step of storing theidentification of the corresponding antenna known by the input point atwhich the response signal is received.

In a variant, the storage consists of positioning a flip-flop in a logicstate and deactivating it when the unit has come into communication withthe portable object detected by the corresponding antenna.

In another variant, the identification of a response signal includes astep of concatenating the identification of the antenna in the responsesignal sent by the antenna.

Another object of the present invention consists of a system ofdetecting portable objects including a network of N antennae associatedwith transmission/reception means and a centralised management unit,principally characterised in that:

-   -   the management unit includes:        -   transmission/reception means connected to the            transmission/reception means of the antennae,    -   the transmission means of the management unit being able to send        signals simultaneously to all the antenna,    -   and the reception means of the said unit being able to receive        the response signals from the antennae which have detected a        portable object, in the form of distinct signals for each        antenna or a resulting signal, according to the type of        connection established between the transmission/reception means        of the management unit and the antennae, and    -   means for successively selecting each portable object detected        according to a pre-established sequence.

The means for successively selecting each portable object detectedaccording to a pre-established sequence include an anti-collisionalgorithm.

According to one embodiment, the transmission/reception means of themanagement unit and the transmission/reception means of the antennae areconnected in point to point mode by connections of the serialtransmission type.

According to another embodiment, the transmission/reception means of themanagement unit include an input point connected to all the antennae bya connection of the serial transmission type.

In the case of the first embodiment, the management unit includes anantenna discriminator.

BRIEF DESCRIPTION OF THE DRAWINGS

Other particularities and advantages of the invention will emergeclearly from a reading of the description given below with regard to thedrawings, in which:

FIG. 1 depicts the outline diagram of the invention,

FIG. 2 depicts an outline diagram according to a variant of theinvention,

FIG. 3 depicts a first embodiment of the invention,

FIG. 4 depicts a second embodiment of the invention, and

FIG. 5 depicts a third embodiment of the invention.

DETAILED DESCRIPTION

According to the method of the invention, the management unit OG is ableto send simultaneously to all the antennae signals which it transmitsand to receive all the responses from the said antennae in the form of aresulting signal S.

Thus all the antennae are seen by this management unit OG as a singleentity as depicted in FIG. 1.

The management unit OG is also able to successively select the portableobjects detected by the said antennae in order to communicate with them(a function bearing the reference COM), this selection taking place in apre-established sequence.

In practice, the successive selection will be effected by ananti-collision algorithm AL whatever it is.

The anti-collision algorithm AL makes it possible to detect a portableobject amongst Q presented to N antennae.

There are many anti-collision algorithms for making a selectionaccording to a pre-established sequence. This sequence may manage forexample a degree of priority, that is to say it would make it possiblein this case to establish communication with the portable objectpresented to the antenna with the highest priority amongst the Nantennae which had detected a portable object.

The algorithm can also allow communication between the management memberand a portable object according to a serial number given in an arbitraryfashion to the antennae and defined by the configuration of the system.

FIG. 2 illustrates a variant of the method according to the invention.

In this variant provision is made for each antenna from A1 to AN to beable to detect one or more objects. This variant in no way changes theprinciple of the invention. Provision is also made for the connectionbetween the antennae and the management unit to be of the point to pointtype, as will be seen in more detail with regard to FIG. 3.

To this end the management unit adds the incoming signals so as to seethe entire network of antennae as a single entity. This unit receivesall the responses S1, S2 to SN from the antennae which have eachdetected the presence of one or more portable objects and forms aresulting signal S. The anti-collision algorithm will enable the unit tomanage the simultaneous arrival of the responses from the network ofantennae.

The advantage of the invention is that the concept of scrutiny of thestate of the art disappears completely.

Because of this, the time required for establishing communication with aportable object presented in front of any antenna no longer depends onthe number of antennae present on the network, but solely on the numberof portable objects presented simultaneously and the performance of theanti-collision algorithm.

Another consequent advantage of this invention concerns the possibilityof managing priorities. The concept of priority is valid both for theselection of an antenna and for the selection of a portable object.

Finally, this solution does not require multiplication of the number ofmanagement units in order to guarantee the performance of a detectionsystem in a network of antennae.

A description will now be given of three embodiments corresponding toimplementation systems with different configurations and able to respondto applications which may be different.

The first embodiment is shown in FIG. 3.

In this embodiment, there is a system connected with the network ofantennae in point to point mode. The connection can be an RS485 or RS422or RS232 or other link.

The management system TG includes the management unit OG strictlyspeaking provided with the intelligence for processing and analysing theinformation received from the portable objects. The management unitsimultaneously interrogates all the antennae of the array in order todetect the presence of a portable object. This is represented by all thesignals E transmitted at the outputs O1–ON by the transmission/receptiondevice ER1 of the management system TG.

The responses received from the network of antennae are represented bythe signals R coming from the transmission/reception circuits ER2 of thenetwork of antennae and arriving at the inputs I1–IN.

Naturally each antenna has its own transmission/reception circuit, butthis is shown here schematically in the form of a block, this blockillustrating the complete equipment of the network of antennae.

When a portable object A or B is present on any one of the antennae, theinformation is sent back to the management unit via an antennadiscrimination device D which receives all the response signals from thesaid antennae by means of the input points D1 to DN.

The role of this device D is to collect this set of information issuingfrom the antennae and to transmit a resulting signal S to the managementunit, whilst enabling it to know the origin thereof.

In the example illustrated in this FIG. 3, the antenna A2 has detected aportable object B which has been selected by the anti-collisionalgorithm AL.

In a practical manner, the antenna discrimination device D hashard-wired logic comprising for example a set of RS flip-flops and anadding device AD. One RS flip-flop is allocated to each antenna in thenetwork.

If, in response to the simultaneous transmission of signals to thenetwork of antenna, several antennae see a return portable objectdetection signal, the RS flip-flops allocated to these antennae are setto 1, which makes it possible to identify the origin of the returnsignal, that is to say the antenna which transmitted this signal.

The discriminator D consequently makes it possible to give theidentification number of the antenna to the management unit, which willenter into communication with the portable object detected by the saidantenna.

The management unit will enter into communication with a selectedportable object and reset to zero the state of the RS flip-flopcorresponding to the antenna which detected this portable object.

This embodiment is particularly adapted to applications such as accesscontrol in a building having entry doors to control and manage and themanagement of the rights allocated to the different individuals enteringthis building. This embodiment makes it possible in fact to managepriorities according to the entry doors and the rights allocated to thepeople entering.

A description will now be given of the second embodiment illustrated bythe diagram in FIG. 4.

In this embodiment the connection between the management unit and thenetwork of antennae is for example effected by an I2C bus. Thetransmission/reception equipment ER1 is of the open collector type inorder to superimpose all the response signals S1–SN arriving at theinput point I of the management system TG.

The management unit OG is also provided with an anti-collision algorithmAL and intelligence for processing and analysing the informationreceived from the portable objects.

As in the previous case, the management unit makes it possible tosimultaneously interrogate all the antennae in the network from itsoutput point O, in order to detect the presence of a portable object.

This embodiment also makes it possible to identify the antennae in thenetwork.

Another difference compared with the embodiment which has just beendescribed with regard to FIG. 3 is that the identification of theantenna is effected by a logic L, conventional per se, placed in eachantenna.

In the case of this second embodiment, the anti-collision algorithm isused by the management unit as soon as a return signal received by thetransmission/reception system ER1 is received at its input port.

The equipment ER1 in this case makes it possible to supply the resultingsignal S to the management unit.

This is because, according to the technology of the equipment, it ispossible to have a single input port I at the management unit connectedby a connection of the serial transmission type to all the antennae inthe network.

This connection will for example be effected by an I2C bus. Thetechnology of the equipment is an open collector technology, whichallows the addition of all the response signals transmitted.

Thus, when a portable object is detected on any one of the antennae, theinformation is sent back directly to the management unit.

The management unit can know the origin of the information since eachantenna and more particularly the logic L which each antenna has makesit possible to concatenate the identification information of the saidantennae with the messages sent in response to the signals transmittedby the management unit.

By way of example, illustrated by FIG. 4, the antenna AN has detected aportable object A selected by the anti-collision algorithm AL in orderto enter into communication with this portable object.

This second embodiment covers the same applications as the embodimentdepicted by FIG. 3.

A third embodiment is illustrated by the diagram in FIG. 5.

In this embodiment there is the same type of connection between themanagement unit and the antenna network, that is to say a connection ofthe parallel transmission type with for example an I2C bus. Thetransmission/reception equipment ER1 of the management unit has atechnology of the open collector type allowing the addition of responsesignals received at the input I so as to supply a resulting signal S tothe management unit itself.

The management unit contains the anti-collision algorithm and theintelligence for processing and analysing the information received fromthe portable objects.

In the same way as in the embodiments described above, this unitsimultaneously interrogates all the antennae in the network in order todetect the presence of a portable object.

This embodiment is particularly adapted to the case where it is notnecessary to know the origin of the information of the received signals.

It applies particularly in the fields of application such as motorwaytolls, anti-theft gates, time stamping (time clock), parking and thecounting of objects, etc.

In the example illustrated in this FIG. 5, it can be seen that aportable object B has been selected by one of the antennae in thenetwork by the anti-collision algorithm AL.

As has just been seen, the management proposed by the invention does nothave recourse to scrutiny and has the following advantages:

-   -   the response time of the system to the presentation of an object        is independent of the number of antennae,    -   the complexity of the management unit is independent of the        number of antennae,    -   any type of anti-collision algorithm can be used for        implementing this method,    -   the management unit does not need to know the number of antennae        installed in the network,    -   the intelligence of the antennae can be eliminated completely.

The invention applies to any type of contactless portable object of theISO 14443-A and ISO 14443-B type, tags (electronic label), operating atfrequencies of 13.56 MHz or 125 kHz.

1. A method of detecting portable objects using a network of N antennae,controlled by a centralized management unit, comprising the followingsteps: transmitting signals simultaneously to all the antennae from saidmanagement unit, receiving response signals from the antennae which havedetected a portable object respectively at an input port of saidmanagement unit that is assigned to each antenna, and adding saidsignals to form a resulting signal, and successively selecting eachobject detected from this resulting signal, according to apre-established sequence.
 2. A detection method according to claim 1,wherein the successive selection of each object is effected by the useof an anti-collision algorithm.
 3. A detection method according to claim1, wherein the reception of the resulting signal includes a step ofidentifying the origin of the response signals forming said resultingsignal.
 4. A detection method according to claim 3, wherein theidentification of a response signal includes a step of storing theidentification of the antenna associated with the input port at whichthe response signal is received.
 5. A detection method according toclaim 4, wherein said storing step includes positioning a flip-flop in alogic state and deactivating it when the unit has entered intocommunication with the portable object detected by the correspondingantenna.
 6. A system of detecting portable objects including a networkof N antennae associated with transmission/reception means and acentralized management unit, comprising: transmission means in themanagement unit that is connected to transmission/reception means of theantennae and that sends signals simultaneously to all the antennae,reception means in said unit that is connected to saidtransmission/reception means and that receives response signals from theantennae which have detected a portable object, in the form of distinctsignals for each antenna respectively at an input port of saidmanagement unit that is assigned to each antenna, and adds said signalsto form a resulting signal, and means for successively selecting eachportable object detected according to a pre-established sequence.
 7. Adetection system according to claim 6, wherein the means forsuccessively selecting each portable object detected in apre-established sequence includes an anti-collision algorithm.
 8. Adetection system according to claim 6 wherein the transmission andreception means of the management unit and the transmission/receptionmeans of the antenna are connected in point-to-point mode by connectionsof the serial transmission type.
 9. A detection system according toclaim 8, wherein the management unit includes an antenna discriminator.